Investments (excluding Consolidated Investment Entities) - Unrealized Capital Losses (Details) $ in Millions	Mar. 31, 2020 USD ($) security	Dec. 31, 2019 USD ($) security
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve months or less below amortized cost, Fair Value	$ 11,879	$ 1,823
Twelve months or less below amortized cost, Unrealized Capital Loss	$ 1,293	$ 21
Twelve months or less below amortized cost, total number of securities in an unrealized loss position | security	1,899	334
More than twelve months below amortized cost, Fair Value	$ 702	$ 1,450
More than twelve months below amortized cost, Unrealized Capital Loss	$ 161	$ 70
More than twelve months below amortized cost, total number of securities in an unrealized loss position | security	227	338
Total, Fair Value	$ 12,581	$ 3,273
Total Unrealized Capital Losses	$ 1,454	$ 91
Total number of securities in an unrealized loss position | security	2,126	672
U.S. Treasuries
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve months or less below amortized cost, Fair Value		$ 2
Twelve months or less below amortized cost, Unrealized Capital Loss		0
More than twelve months below amortized cost, Fair Value		21
More than twelve months below amortized cost, Unrealized Capital Loss		0
Total, Fair Value		23
Total Unrealized Capital Losses		0
State, municipalities and political subdivisions
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve months or less below amortized cost, Fair Value	$ 66	25
Twelve months or less below amortized cost, Unrealized Capital Loss	$ 3	0
Twelve months or less below amortized cost, total number of securities in an unrealized loss position | security	22
More than twelve months below amortized cost, Fair Value	$ 1	1
More than twelve months below amortized cost, Unrealized Capital Loss	$ 0	0
More than twelve months below amortized cost, total number of securities in an unrealized loss position | security	1
Total, Fair Value	$ 67	26
Total Unrealized Capital Losses	$ 3	0
Total number of securities in an unrealized loss position | security	23
U.S. corporate public securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve months or less below amortized cost, Fair Value	$ 2,350	122
Twelve months or less below amortized cost, Unrealized Capital Loss	$ 288	3
Twelve months or less below amortized cost, total number of securities in an unrealized loss position | security	452
More than twelve months below amortized cost, Fair Value	$ 30	199
More than twelve months below amortized cost, Unrealized Capital Loss	$ 14	16
More than twelve months below amortized cost, total number of securities in an unrealized loss position | security	8
Total, Fair Value	$ 2,380	321
Total Unrealized Capital Losses	$ 302	19
Total number of securities in an unrealized loss position | security	460
U.S. corporate private securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve months or less below amortized cost, Fair Value	$ 1,362	113
Twelve months or less below amortized cost, Unrealized Capital Loss	$ 89	1
Twelve months or less below amortized cost, total number of securities in an unrealized loss position | security	110
More than twelve months below amortized cost, Fair Value	$ 116	195
More than twelve months below amortized cost, Unrealized Capital Loss	$ 41	20
More than twelve months below amortized cost, total number of securities in an unrealized loss position | security	11
Total, Fair Value	$ 1,478	308
Total Unrealized Capital Losses	$ 130	21
Total number of securities in an unrealized loss position | security	121
Foreign corporate public securities and foreign governments
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve months or less below amortized cost, Fair Value	$ 1,078	15
Twelve months or less below amortized cost, Unrealized Capital Loss	$ 112	0
Twelve months or less below amortized cost, total number of securities in an unrealized loss position | security	224
More than twelve months below amortized cost, Fair Value	$ 37	103
More than twelve months below amortized cost, Unrealized Capital Loss	$ 8	6
More than twelve months below amortized cost, total number of securities in an unrealized loss position | security	8
Total, Fair Value	$ 1,115	118
Total Unrealized Capital Losses	$ 120	6
Total number of securities in an unrealized loss position | security	232
Foreign corporate private securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve months or less below amortized cost, Fair Value	$ 2,100	36
Twelve months or less below amortized cost, Unrealized Capital Loss	$ 178	0
Twelve months or less below amortized cost, total number of securities in an unrealized loss position | security	144
More than twelve months below amortized cost, Fair Value	$ 52	78
More than twelve months below amortized cost, Unrealized Capital Loss	$ 11	2
More than twelve months below amortized cost, total number of securities in an unrealized loss position | security	6
Total, Fair Value	$ 2,152	114
Total Unrealized Capital Losses	$ 189	2
Total number of securities in an unrealized loss position | security	150
Residential mortgage-backed
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve months or less below amortized cost, Fair Value	$ 1,870	730
Twelve months or less below amortized cost, Unrealized Capital Loss	$ 145	8
Twelve months or less below amortized cost, total number of securities in an unrealized loss position | security	357
More than twelve months below amortized cost, Fair Value	$ 130	194
More than twelve months below amortized cost, Unrealized Capital Loss	$ 17	6
More than twelve months below amortized cost, total number of securities in an unrealized loss position | security	77
Total, Fair Value	$ 2,000	924
Total Unrealized Capital Losses	$ 162	14
Total number of securities in an unrealized loss position | security	434
Commercial mortgage-backed securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve months or less below amortized cost, Fair Value	$ 1,836	472
Twelve months or less below amortized cost, Unrealized Capital Loss	$ 330	4
Twelve months or less below amortized cost, total number of securities in an unrealized loss position | security	307
More than twelve months below amortized cost, Fair Value	$ 0	18
More than twelve months below amortized cost, Unrealized Capital Loss	$ 0	0
More than twelve months below amortized cost, total number of securities in an unrealized loss position | security	0
Total, Fair Value	$ 1,836	490
Total Unrealized Capital Losses	$ 330	4
Total number of securities in an unrealized loss position | security	307
Other asset-backed securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve months or less below amortized cost, Fair Value	$ 1,217	308
Twelve months or less below amortized cost, Unrealized Capital Loss	$ 148	5
Twelve months or less below amortized cost, total number of securities in an unrealized loss position | security	283
More than twelve months below amortized cost, Fair Value	$ 336	641
More than twelve months below amortized cost, Unrealized Capital Loss	$ 70	20
More than twelve months below amortized cost, total number of securities in an unrealized loss position | security	116
Total, Fair Value	$ 1,553	949
Total Unrealized Capital Losses	$ 218	$ 25
Total number of securities in an unrealized loss position | security	399